Eden Hazard came off the bench to score for Chelsea in their win at Huddersfield.
Photograph: Chris Brunskill/Fantasista/Getty Images

Maurizio Sarri believes Eden Hazard has the ability to establish himself as the best player in the world but has admitted he feared losing the Belgium forward in the three weeks after taking charge as Chelsea’s manager.

Hazard, who came off the bench to set up the final goal in the 3-0 opening weekend win at Huddersfield, is expected to start against Arsenal on Saturday as Sarri oversees his first competitive fixture at Stamford Bridge.

He was Chelsea’s top scorer last season and enjoyed an eye-catching World Cup, captaining Belgium to third place, only to suggest the time might be right “to discover something different”.

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Those comments were made in St Petersburg in mid-July, a few days after Sarri’s appointment and before the 27-year-old player’s departure on holiday, and it was more than three weeks before the manager met Hazard at Chelsea’s training base in Cobham.

“I was concerned about this problem,” said Sarri, aware that the transfer window extends until the end of the month in Spain, where Real Madrid have long coveted Hazard.

“But the first time I spoke to him, I was sure he would stay. So I was concerned for 20 days, no more. Hazard, technically, is really one of the best in Europe in this moment. He has to work from the physical point of view, of course.

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“I have spoken to him very often in the last 10 days but he has never said to me anything about [leaving]. So I am sure Eden will be with us for this season. Why am I sure? Because Chelsea are one of the most important clubs in Europe. I think one of the most important clubs in Europe cannot sell an important player without the possibility of buying a player on the same level.”

Sarri’s predecessor, Antonio Conte, had often suggested Hazard needed to contribute more goals if he was to challenge Cristiano Ronaldo and Lionel Messi for the Ballon d’Or.

“It depends on his position on the pitch,” Sarri said. “In the last five years, Cristiano has played like a striker, Messi like a striker, Eden sometimes like a winger. Eden can improve. We are talking about one of the most important players in Europe but he can improve more. He can be the first. It depends on him. The best for technical skill, the best for scoring but I think it depends only on him. On his mind.”

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While any belated interest from Real this month will be dismissed out of hand, no further progress has been made in talks over a contract. Hazard’s deal expires in 2020. Regardless, the playmaker remains a strong candidate to be named Sarri’s full-time captain at Stamford Bridge, with the manager still deliberating over who will wear the armband as he considers the squad at his disposal. César Azpilicueta will retain the honour against Arsenal, with Gary Cahill also among the candidates. A decision will be made only once Sarri has ascertained his first-choice lineup.

He believes Arsenal will be “competitive” in pursuit of Champions League qualification under Unai Emery this season. “This coach has the ability to start a new era,” he said of Emery. “He won three times the Europa League, and won [trophies] in France, so we’re talking about a very good coach. I think that, in pre-season, they have played well.

“I think Arsenal, this season, can improve and be competitive, and can fight for a good position. They can be, for us, a direct opponent for the target of the club this season. A direct opponent for a place in the Champions League.

“But, for now, all I want is my team to continue to improve their performances. In the first part of the season, it’s very difficult to gain points, so we need to improve performances. That is more important in this moment than the results.”